What began as a Reddit conversation has grown into a movement of scientists and science lovers standing up for evidenced-based policy making and inclusivity in the science community.

The date of the march isn't just an average Saturday. April 22 is Earth Day, first celebrated in 1970.

The original Earth Day is seen by many as a turning point in the environmental movement. The year itself also marks a major turning point for the U.S. government and environmental policy. In 1970, Richard Nixon signed the Environmental Protection Agency into existence and it began operating that December.

The circumstances from the March for Science are a bit different in 2017. For one, it isn't focused solely on environmental science but all disciplines from astronomy to zoology. There's also not a swell of support for science in the federal government. In fact, the march was inspired by a Congress and president that appear hostile to science, particularly in regards to climate change.

Whatever becomes of the march, it won't be the first time scientists have turned out to protest what they view as federal policies ungrounded in science. The 2014 People's Climate March turned out an estimated 310,000 people in New York, including a large number of climate scientists.

Naomi Oreskes, a science historian at Harvard, said that looking further into the past reveals another telling example of scientists organizing.

"It is the scientists who mobilized against the arms race in the late 1950s and 1960s," she said. "So that tells you how scientists feel now. This is an existential threat."